[Tempest1981]

To address slow charging, could you have an array of them, some charging and some discharging? But you would need maybe 7x more then, so they would need to be 7x cheaper to compete. (Not quite sure how the math works out to account for charge rates and weather.)

[hamandcheese]

For that matter, why not have 7x the batteries at 1/7 the capacity? Or does the charge rate not depend on the capacity?

[hwillis]

Charge rate is independent of capacity. A 3 C battery charges in 20 minutes, whether it's 1 kWh or 7 kWh. If you have 7 batteries, each charges in 20 minutes.